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Acid/base solubility

  1. Mar 10, 2008 #1
    i have 5 test tubes with benzoic acid, and i pour NH4OH, NaOH, HCl, NaHCO3 and diethyl ether into different tubes. The first 3 dissolved completely but the last 2 did not. Any ideas why?
    i dont believe "like dissolves like" applies here since they are all polar.
     
    Last edited: Mar 10, 2008
  2. jcsd
  3. Mar 10, 2008 #2

    symbolipoint

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    I would be curious about how the basic dissociation constant of NaHCO3 compares to that of NH4OH. Check the handbook information. I'm not sure at the moment why the bicarbonate ion would not neutralize the benzoic acid; benzoic acid itself may be too weak an acid to add a proton to the bicarbonate ion. The Ammonia (solution in water) and the NaOH are both strong enough bases to neutralize the benzoic acid; and generally, Na+ salts and ammonium salts are soluble.
     
  4. Mar 10, 2008 #3
    [tex]K_B(NH_4OH) = 1.8\cdot10^{-5}[/tex]

    [tex] K_B(HCO_3^-) = 2.3\cdot10^{-8}[/tex]

    So NaHCO3 is about 1000 times less basic than ammonia.
    Benzoic acid is a solid made of polar molecules, so it dissolves quite well in polar solvents as water and acetone and not in non-polar as diethyl ether.
     
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